The present disclosure relates to the subject matter contained in Japanese Patent Application No.2002-104242 filed on Apr. 5, 2002, which is incorporated herein by reference in its entirety.
1. Field of the Invention
This invention relates to a connector for connection to a cable having a shielding conductor such as a coaxial cable, and more particularly to a high-frequency connector, which achieves the characteristic impedance matching with a transmission path and can be easily mounted on and connected to a cable end.
2. Description of the Related Art
In recent years, electrical signals have been adapted to be transmitted at high speed (high frequency) to a control-purpose printed circuit board having electronic parts, ICs (Integrated Circuits) and the like contained in an automotive electrical equipment such as a car navigation system. In addition, circuit patterns on such a printed circuit board have been densely arranged to provide a high-density design. Generally, a coaxial cable is used for transmitting such a high-frequency electrical signal and with the higher-frequency transmission of the electrical signal, the connector for connection to this coaxial cable has been required to have a compact design meeting with the high-frequency transmission.
Referring to a common structure of a coaxial cable, the coaxial cable has a coaxial structure in which an insulator is interposed between a signal conductor (serving as a transmission path for an electrical signal or the like) including a plurality of metal wires twisted together into a bundle and a shielding conductor including a braided wire having a plurality of woven wires. The outer periphery of this structure is covered with an insulating sheath. The shielding conductor covers the outer peripheral surface of the signal conductor with a predetermined gap therebetween completely over the entire periphery thereof, so that this structure is suited for transmitting a high-frequency electrical signal.
Generally, a coaxial connector, which contains terminals and is connected to each of both ends of such a coaxial cable for transmitting a high-frequency signal, includes an inner conductor terminal, an outer conductor terminal, and a dielectric member. The inner conductor terminal is connected to the signal conductor of the cable. The outer conductor terminal is connected to the shielding conductor such as a braided wire and covers the outer periphery of the inner conductor terminal to electromagnetically shield the inner conductor terminal. The dielectric member having a predetermined dielectric constant is interposed between the inner conductor terminal and the outer conductor terminal. The inner conductor terminal and the outer conductor terminal are electrically connected separately respectively to the signal conductor and the shielding conductor, which are exposed at the cable end to be connected to the connector by removing the sheath and the insulator therefrom.
When the characteristic impedance of a coaxial cable for transmitting a high-frequency electrical signal does not coincide with the characteristic impedance of each of coaxial connectors connected to both ends of this cable, respectively, the reflection of the signal occurs. This reflection causes noises and besides the transfer of energy is wasted. Therefore, it is necessary to achieve the impedance matching between the coaxial connector and the coaxial cable usually by setting the impedance value, for example, to 50xcexa9. With respect to the characteristic impedance of the coaxial connector, generally, xe2x80x9ca ratio of an inner diameter of a cross-section of the outer conductor terminal to an outer diameter of a cross-section of the inner conductor terminalxe2x80x9d and xe2x80x9cthe dielectric constant of the dielectric memberxe2x80x9d are adjusted to achieve the impedance matching with a coaxial cable to be connected to the coaxial connector. If the inner conductor terminal within the coaxial connector has any portion, which is not covered with the outer conductor terminal, there is encountered a problem that the shielding performance such as radiation characteristics is lowered. Therefore, it is preferred that the inner conductor terminal should be covered with the outer conductor terminal completely over the entire periphery thereof.
One high-frequency coaxial connector is disclosed in JP-A-2000-260540. This connector is so designed that at a time of mounting the connector on the coaxial cable to connect the connector, cutting of the signal conductor of the coaxial cable and an eccentric arrangement of the inner conductor terminal of the connector with respect to the coaxial cable are prevented.
A process of mounting this coaxial connector on the coaxial cable includes the following steps: i) exposing the signal conductor and a shielding conductor over a predetermined length by peeling a sheath from an end portion of the coaxial cable; ii) press-fastening a press-clamping portion of the inner conductor terminal to the signal conductor; iii) inserting a separately-prepared sleeve between an insulator and the shielding conductor; iv) fitting an outer conductor terminal to the coaxial cable and attaching a dielectric member to the inner conductor terminal; v) subsequently returning the fitted outer conductor terminal to cause this outer conductor terminal to receive the dielectric member therein; and vi) finally press-fastening a press-clamping portion of the outer conductor terminal to the cable.
However, in the coaxial connector disclosed in the JP-A-2000-260540, an opening portion in a rear end of the outer conductor terminal is made large in order to prevent the signal conductor from being cut when returning the outer conductor terminal to cause it to receive the dielectric member attached to the inner conductor terminal. Therefore, the impedance matching with the coaxial cable and the shielding performance were not excellent.
Furthermore, the connector of this structure has a problem with the manner of mounting the connector on the cable. Namely, most of the above mounting steps must be carried out manually and the ratio of its production cost to its product price is higher as compared with those connectors mounted on the cable by a highly-automated process. Therefore it has been difficult to provide this connector at low costs.
An object of this invention is to provide a coaxial connector in which the impedance matching in the coaxial connector is achieved to reduce the noise radiation amount, the reflection loss of a signal and the like, and a process of mounting the connector on a cable end can be carried out efficiently.
To solve the above problems, there is provided a coaxial connector for a coaxial cable having a signal conductor, a shielding conductor, an insulator disposed between the signal conductor and the shielding conductor, and a sheath covering an outer periphery thereof. The coaxial connector includes an inner conductor terminal, a dielectric member, an outer conductor terminal, and a shielding member. The inner conductor terminal is connected to the signal conductor. The outer conductor terminal of a cylinder shape, receives the inner conductor terminal through the dielectric member. The outer conductor terminal is connected to the shielding conductor. The outer conductor terminal includes a first opening, a side wall, and a convex wall. The convex wall is formed at a position opposed to a connection portion between the exposed signal conductor and the inner conductor terminal, to project toward inside thereof. The shielding member is attached to the outer conductor terminal to close the first opening.
A sectional area of the first opening closed by the shielding member may be smaller than that of other portion of the outer conductor terminal.
The convex wall may be formed to reduce a sectional area of the first opening.
In the coaxial connector of the above construction, the cross-sectional area of the outer conductor terminal at a connecting portion where the signal conductor of the coaxial cable and the inner conductor terminal are connected together is reduced in accordance with the cross-sectional area of the signal conductor at the connecting portion, thereby achieving the impedance matching. The first opening is formed on the outer conductor terminal to receive the inner conductor terminal. The convex wall is formed to reduce a sectional area of the first opening. As a result, the characteristic impedance in the neighbor of the connecting portion between the signal conductor and the inner conductor terminal is reduced so that it is possible to match the impedance. In addition, the inner conductor terminal, which has already been connected to the signal conductor, can be inserted into the dielectric member, which is received inside the outer conductor terminal in advance, by utilizing the first opening of the outer conductor terminal. Therefore, the insertion of the inner conductor terminal by utilizing the first opening can be easily effected in an automated manner by the use of a machine. Namely, as compared with the coaxial connector according to the related art, which has been manually mounted on the cable, the production cost can be reduced. The shielding member may close the first opening. Therefore, the lowering of the shielding performance is small.
In this case, when the shielding member is attached in a position where the cross-sectional area of the first opening is reduced, the high characteristic impedance in the vicinity of the connecting portion between the inner conductor terminal and the signal conductor can also be decreased using the shielding member. Therefore, using this construction and the matching convex portion in combination, it becomes possible to adjust the characteristic impedance in the vicinity of the connecting portion between the inner conductor terminal and the signal conductor. Thus, this facilitates the design of the connector.
In addition, the shielding member may be attached to the outer conductor terminal to engage with the side wall of the first opening. With this construction, the shielding member can be mounted on the outer conductor terminal at other portion than a portion closing the opening portion. Therefore, the opening portion can be fully closed.
The outer conductor terminal may further integrally include a sleeve for covering the shield conductor of the coaxial cable. The shielding member may include a press-clamping portion, which is press-fixed to a portion of the sleeve, which the shielding conductor covers. With this construction, it is not necessary to separately provide a sleeve for preventing the deformation of the cable as described above in the xe2x80x9cBackground of the inventionxe2x80x9d. This prevents the number of the component parts of the connector from increasing. Thus, the press-clamping portion for clamping engagement with the cable, which is formed integrally on the outer conductor terminal in the related art, is eliminated. This portion is formed into the sleeve portion for preventing the deformation of the cable. Instead, the press-clamping portion for clamping engagement with the cable is formed on the shielding member. With this construction, the process of mounting the connector on the cable can be carried out in an automated manner by a machine. Namely, the production cost required for mounting the connector on the coaxial cable can be reduced as compared with the related art in which manual assembly is conducted.
The coaxial connector may further include a connector housing. The shielding member may include a stabilizer serving as a guide when the connector housing is attached. Alternatively, the shielding member may include a stabilizer protruding therefrom outwardly. With either construction, it is not necessary to provide a stabilizer on the outer conductor terminal. Therefore, the outer conductor terminal is prevented from being formed into a complicated shape. In addition, the coaxial connector may further include a connector housing having a retainer. The shielding member may include a stabilizer for engaging with the retainer. With this construction, the detachment of the connector from the connector housing is prevented. Furthermore, the coaxial connector may further include a connector housing having a lance for engaging with a second opening portion formed by protruding the convex wall. With this construction, the detachment of the coaxial connector from the connector housing is prevented. Also, when the connector is retained within the connector housing by the double-retaining function provided by the lance and the retainer, the coaxial connector is prevented from being wrenched within the connector housing, and damage of the connector is prevented.
According to another aspect of the invention, there is provided a coaxial connector for a coaxial cable having a signal conductor, a shielding conductor, a insulator disposed between the signal conductor and the shielding conductor, and a sheath covering an outer periphery thereof. The coaxial connector includes first and second connectors. The first connector includes an inner conductor terminal, a dielectric member, an outer conductor terminal, and a shielding member. The inner conductor terminal of a female terminal shape, is connected to the signal conductor. The outer conductor terminal of a cylinder shape, receives the inner conductor terminal through the dielectric member. The outer conductor terminal is connected to the shielding conductor. The second connector includes an inner conductor terminal and an outer conductor terminal. The inner conductor terminal of a male terminal shape, is connected to the inner conductor terminal of the first connector. The outer conductor terminal of the first connector includes an opening, a side wall, and a convex wall. The convex wall is formed at a position opposed to a connection portion between the exposed signal conductor and the inner conductor terminal, to project toward inside thereof. The shielding member of the first connector is attached to the outer conductor terminal of the first connector to close the opening portion of the first connector. The end portion of the dielectric member of the first connector has smaller diameter than an end portion of the outer conductor terminal of the second connector. An air layer is defined between the dielectric member of the first connector and the outer conductor terminal of the second connector when the first and second connectors are connected to each other. With this construction, the disturbance of the characteristic impedance can be eliminated also at a region where the first and second connectors are connected.
In this case, a rib extending in a longitudinal direction may be formed on the dielectric member of the first connector. With this construction, the strength of the dielectric member is increased. In addition, a guide surface of a tapered shape may be formed on the end portion of the dielectric member of the first connector. With this construction, the smooth fitting operation can be effected.